1. Field of the Invention
The present invention relates to a signal receiving device and method, especially to a wireless signal receiving device and method.
2. Description of Related Art
Signals to be processed in a baseband circuit are usually at a lower frequency for operation consideration and power conservation, but signals to be sent through wireless transmission are usually carried on a higher frequency for the prevention of transmission loss; accordingly, baseband signals of lower frequency will be up-converted into radio signals of higher frequency by a radio-frequency (RF) circuit before wireless transmission, and radio signals of higher frequency will be down-converted into baseband signals of lower frequency by the RF circuit for baseband operation. Take the reception of satellite positioning signals for example. The frequency of a common satellite positioning signal is normally above 1.5 GHz; during the reception process, the satellite positioning signal will be down-converted into an intermediate-frequency (IF) signal (whose frequency is normally at dozens of MHz) first after it is received by an RF circuit, and then down-converted into a baseband signal (whose frequency is normally between several MHz and tens of MHz). However, if a satellite positioning signal receiver is applicable to several kinds of satellite position systems (e.g. Global Positioning System (GPS) of United States, Galileo Positioning System (Galileo) of Europe, Global Navigation Satellite System (Glonass) of Russia, and Beidou/Compass Navigation Satellite System (Beidou) of China), in view of the signal frequencies of different satellite positioning systems (e.g. GPS system, Glonass system and Beidou system) are distinct, the satellite positioning signal receiver is usually equipped with several sets of local oscillators and mixers to be able to take care of all types of the concerned satellite signals, and generate appropriate IF signals. Although the above-mentioned solution is straight, it unavoidably leads the increase of cost of the receiver. Other prior arts could be found in the discussion of the reference: “Wireless Transceivers of Smart Devices”, Session 19, ISSCC, 2013.
Additionally, the foresaid radio signals need to go through a sampling process of analog-to-digital conversion to be converted into baseband signals. According to Nyquist Theorem, the sampling frequency has to be at least two times the maximum frequency of the signal to be sampled, so as to reconstruct the waveform of the signal to be sampled properly, or else the sampled result will suffer aliasing which means that the sampled result will be associated with an image frequency instead of the actual frequency of the signal to be sampled. However, a high sampling frequency will require significant circuit capability and power consumption of an analog-to-digital converter, which consequently leads to a high cost.